[PATCH AUTOSEL 6.13 12/21] scsi: core: Use GFP_NOIO to avoid circular locking dependency

Sasha Levin
2025-02-11T01:30:22Z

From: Rik van Riel <riel@surriel.com>

[ Upstream commit 5363ee9d110e139584c2d92a0b640bc210588506 ]

Filesystems can write to disk from page reclaim with __GFP_FS
set. Marc found a case where scsi_realloc_sdev_budget_map() ends up in
page reclaim with GFP_KERNEL, where it could try to take filesystem
locks again, leading to a deadlock.

WARNING: possible circular locking dependency detected
6.13.0 #1 Not tainted
------------------------------------------------------
kswapd0/70 is trying to acquire lock:
ffff8881025d5d78 (&q->q_usage_counter(io)){++++}-{0:0}, at: blk_mq_submit_bio+0x461/0x6e0

but task is already holding lock:
ffffffff81ef5f40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x9f/0x760

The full lockdep splat can be found in Marc's report:

https://lkml.org/lkml/2025/1/24/1101

Avoid the potential deadlock by doing the allocation with GFP_NOIO, which
prevents both filesystem and block layer recursion.

Reported-by: Marc Aurèle La France <tsi@tuyoix.net>
Signed-off-by: Rik van Riel <riel@surriel.com>
Link: https://lore.kernel.org/r/20250129104525.0ae8421e@fangorn
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/scsi_scan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 042329b74c6e6..fe08af4dcb67c 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -245,7 +245,7 @@ static int scsi_realloc_sdev_budget_map(struct scsi_device *sdev,
}
ret = sbitmap_init_node(&sdev->budget_map,
scsi_device_max_queue_depth(sdev),
- new_shift, GFP_KERNEL,
+ new_shift, GFP_NOIO,
sdev->request_queue->node, false, true);
if (!ret)
sbitmap_resize(&sdev->budget_map, depth);
--
2.39.5